Mobile devices (e.g., smartphones) use embedded sensors, for example, global positioning system (GPS), accelerometer, Bluetooth®, and Wi-Fi, as well as increased capability in computation (e.g., CPU performance, battery life, and memory size). Among these various sensors, Bluetooth® is relatively more stable and less expensive because of low cost, less constraints (both indoor and outdoor), and less battery drain as compared to other sensors, such as GPS and Wi-Fi.
Bluetooth® sensors are typically used for exchanging files between devices within a short distance from one another, indoor location positioning by combining Bluetooth® and Wi-Fi signals, and estimating nearby device/people population in a crowd.